Browning evergreens mark the unofficial end of the holiday season and cause headaches for the city sanitation workers responsible for clearing the streets.

The New York City Department of Sanitation will dispatch special Christmas tree-only collection routes from January 5 to January 16. Trees picked up on those days that are stripped of all decorations will be fed through a woodchipper and turned into mulch for use in city parks.

Some garbage collectors say they would like to see those dates extended for at least two weeks because of the number of Christmas trees placed curbside after the specified recycling days. Trees thrown out before January 5 or after January 16 will be taken to the dump.

An Upper East Side sanitation worker, Domenick Mistretta, said that trees discarded after the mid-January deadline take up space and weight on the 13-ton collection trucks. Mr. Mistretta, 34, said the trucks can fill up before the morning garbage pick-up route is complete — forcing the sanitation department to send out another team of garbage collectors later in the day. “It’s just impossible,” he said. “There can be hundreds of trees. I hear guys complaining that there are just so many trees that they just can’t finish their routes.”

Another sanitation worker in the neighborhood, Thomas Libretti, 49, said collecting trash in January can be “a living hell” because there are so many old Christmas trees to collect. Mr. Libretti, who said it’s not usual to see trees curbside into February, stressed the importance of promptly removing the trees from city streets because they are potential fire hazards. “When they’re dried up, it only takes one cigarette butt to set it on fire,” he said.

Last year, the sanitation department handed over to the New York Department of Parks and Recreation more than 157,000 Christmas trees — weighing some 1,300 tons — for recycling. The city began the Christmas tree recycling program 14 years ago, according to a sanitation department spokesman, Keith Mellis, He said the department does not keep a tally of the number of trees taken to the dump each year.

An additional 8,800 trees were recycled as part of MulchFest, when city residents can bring their trees to designated city parks and, in many cases, take home wood chips to be used as mulch. MulchFest, sponsored by the parks department, takes place from 10 a.m. to 2 p.m., Saturday, January 6, and Sunday, January 7, in 66 city parks throughout the five boroughs. Mulch helps prevent soil erosion and control weed growth.

Mr. Mellis said posters on garbage trucks, and public service announcements on the city’s 311 information hotline inform city residents of the recycling program.

Earlier this month, the sanitation department issued 10 tips for reducing waste during the holiday season. The department recommends buying an artificial tree that can be used year after year; wrapping gifts in reusable bags, old maps, or comic strips, or giving gifts that don’t need to be wrapped in paper, such as homemade cookies, a charitable donation, museum memberships, concert tickets, or a gift certificate for a spa treatment.